1. Field of the Invention
The present invention relates to a tag for theft prevention. More specifically, the invention relates to a tag for theft prevention which is used for preventing a recording medium from being taken away unjustly from a shop. The tag for theft prevention is provided inside a container case containing a recording medium such as a compact disk (CD), a mini disk (MD), a digital video disk (DVD) or a video tape, or provided on a protective case covering a container case for preventing the container case from being damaged. As a result, when a container case or a protective case which is displayed on displaying shelves, etc. in a retail shop and a rental video shop, etc. passes between a transmitting antenna and a receiving antenna to be taken away, the tag is detected so as to prevent the recording medium from being taken away unjustly.
2. Description of the Related Art
In order to prevent theft of a recording medium from a shop, a sheet-type tag, for example, is directly stuck to a container case of a recording medium or a sheet-type tag stuck to a transparent sheet is put in a transparent bag together with a compact disk (CD) being an example of the recording medium. However, neither of the above-described cases is complete because a tag is pealed off or a transparent sheet is drawn out. The related art is further described with reference to a CD as an example.
In order to overcome this problem, a sheet-type tag is stuck inside a protective case having a locking mechanism and then a container case containing a CD is fixed inside the protective case to make it impossible to have the sheet-type tag stuck to inside the protective case pealed off and prevent the CD from being taken away unjustly. Further, the container case containing the CD (goods) is handed to a purchaser after the locking mechanism is released when the purchaser takes the protective case containing the container case to, for example, a cashier and pays the price.
The above-described container case (hereinafter referred to as a "CD case") consists of transparent plastic so that titles of music and commentaries inside the above-described container case can be read and the protective case consists of transparent plastic so that titles of music and commentaries inside the CD case can be read through the protective case as well.
The above-described tag is provided with a resonating circuit comprising a coil arranged in a curled or coiled state and a capacitor arranged in the central portion of the coil while connected to the coil and a cover made of thin paper for hiding both inside and outside of the coil and the capacitor and is structured so that it can be stuck and fixed inside the protective case by a sticking portion provided on one of both sides of the above-described cover made of paper.
When a sticker-type tag is stuck inside a CD case as described above, a specific portion of the CD case corresponding to the portion to which the sticker-type tag is stuck is covered and titles of music and commentaries, etc. of the specific portion inside the CD case cannot be seen, which causes an inconvenience disadvantageous to a shop such as a decline of purchasing volition of some purchasers. Further, since the number of windings of a coil must be multiple in order to secure the detection sensitivity to a certain extent, the above-described portion to be covered becomes inevitably large and promotes the above-described inconvenience and therefore there has been room to improve.
Further, an aluminum evaporated CD affects the detection sensitivity of a sticker-type tag adversely because the sticker-type tag stuck inside a protection case overlaps with the CD on the thickness direction, which causes the decrease of the detection sensitivity of the sticker-type tag as well. Incidentally, although it can be considered to stick a sticker-type tag to inside the protective case so that the sticker-type tag is placed on the surface of the corner portion of a CD case, since the sticker-type tag has relatively large size as described above, the sticker-type tag cannot be contained in the corner portion of the CD case and there inevitably is a portion overlapping the CD, which has made it impossible to avoid the decrease of the detection sensitivity of the above-described sticker-type tag.
In addition, since the above-described sticker-type tag has directivity, it cannot be detected in some cases depending on an angle in passing between the transmission antenna and the receiving antenna, which has left room to improve.